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Question 1
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
50% (03:21) correct
50%
(02:55) wrong
based on 147
sessions
History
Date
Time
Result
Not Attempted Yet
Question 2
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
53% (01:12) correct 47%
(01:22) wrong
based on 131
sessions
History
Date
Time
Result
Not Attempted Yet
Question 3
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
61% (00:57) correct 39%
(01:12) wrong
based on 135
sessions
History
Date
Time
Result
Not Attempted Yet
Question 4
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
77% (01:04) correct 23%
(01:16) wrong
based on 130
sessions
History
Date
Time
Result
Not Attempted Yet
Sound travels through the air in waves from a central source much as ripples from a pebble dropped into a pond travel across the surface of the pond, diminishing in intensity as they move away from the source. The speed at which sound waves travel in the air is affected by the air temperature, but for most purposes we can consider the speed of sound to be relatively constant at 1,100 feet per second. The distance between the peaks of the waves is the wavelength of the sound just as the distance between the ripples in the pond is the wavelength of the water. If we continue with the ripple-in-the-pond analogy and imagine a cork floating on the surface of the water, we can think of the frequency of sound waves as the number of times the cork bobs up and down during a given interval as the waves of water pass it in two dimensions.
The frequency is simply the speed of propagation of the wave divided by its wavelength. Therefore, if a sound is created at a given point, a system of spherical waves propagates from that point outward through the air at a speed of 1,100 feet per second, with the first wave making an ever-increasing sphere with time. On that sphere, the sound energy remains essentially constant in an ideal case. As the wave spreads, the height of the wave or the intensity of the sound at any given point must diminish as the fixed amount of energy is spread over the increasing surface area of the sphere. This phenomenon is known as the geometric attenuation of the sound. If we placed monitoring stations along the path of propagation of the sound, we would find that the intensity of the sound near the source would be much higher than the intensity of the sound at a great distance due to this phenomenon. Mathematical relationships have been derived to describe this geometric attenuation, according to which for every doubling of distance the sound level will decrease by 6 decibels (dB). In other words, if station I were at a distance of 50 feet from the point source, and if station 2 were 100 feet from the point source, the sound level measured at station 2 would be 6 dB less than the sound level measured at station 1.
This kind of relationship holds true when the sound source is a single vehicle or an aircraft and when sound is propagating in free air, either from an airplane to the ground in completely spherical propagation or, in the case of an automobile on the ground, when the propagation field is only half a sphere. When a number of vehicles are lined up and constitute a continuous stream of noise sources, the situation is no longer characterized by a spherical or hemispherical spreading of the sound. Instead, the reinforcement by the line of point sources makes the propagation field more like a cylinder or half-cylinder. In this case, the decrease in sound for each doubling of the distance from the line source is only 3 decibels.
The frequency is simply the speed of propagation of the wave divided by its wavelength. Therefore, if a sound is created at a given point, a system of spherical waves propagates from that point outward through the air at a speed of 1,100 feet per second, with the first wave making an ever-increasing sphere with time. On that sphere, the sound energy remains essentially constant in an ideal case. As the wave spreads, the height of the wave or the intensity of the sound at any given point must diminish as the fixed amount of energy is spread over the increasing surface area of the sphere. This phenomenon is known as the geometric attenuation of the sound. If we placed monitoring stations along the path of propagation of the sound, we would find that the intensity of the sound near the source would be much higher than the intensity of the sound at a great distance due to this phenomenon. Mathematical relationships have been derived to describe this geometric attenuation, according to which for every doubling of distance the sound level will decrease by 6 decibels (dB). In other words, if station I were at a distance of 50 feet from the point source, and if station 2 were 100 feet from the point source, the sound level measured at station 2 would be 6 dB less than the sound level measured at station 1.
This kind of relationship holds true when the sound source is a single vehicle or an aircraft and when sound is propagating in free air, either from an airplane to the ground in completely spherical propagation or, in the case of an automobile on the ground, when the propagation field is only half a sphere. When a number of vehicles are lined up and constitute a continuous stream of noise sources, the situation is no longer characterized by a spherical or hemispherical spreading of the sound. Instead, the reinforcement by the line of point sources makes the propagation field more like a cylinder or half-cylinder. In this case, the decrease in sound for each doubling of the distance from the line source is only 3 decibels.
1. In the analogy of a ripple in a pond to a sound in the air drawn in the first paragraph of the passage, the floating cork is analogous to:
A. a solid medium that retards sound propagation
B. a sound-frequency monitoring device
C. an object on which a sound is likely to echo
D. the source of a particular sound
E. a sound wave moving through space
A. a solid medium that retards sound propagation
B. a sound-frequency monitoring device
C. an object on which a sound is likely to echo
D. the source of a particular sound
E. a sound wave moving through space
2. According to the passage, sound waves and water waves are similar in all of the following ways EXCEPT:
A. Each forms a sphere of ever-increasing size.
B. Each is characterized by a particular wavelength.
C. Each is propagated outward from a central source.
D. Each is characterized by a particular wave frequency.
E. Each is characterized by a diminishing average strength at greater distances from the source.
A. Each forms a sphere of ever-increasing size.
B. Each is characterized by a particular wavelength.
C. Each is propagated outward from a central source.
D. Each is characterized by a particular wave frequency.
E. Each is characterized by a diminishing average strength at greater distances from the source.
3. The intensity of a sound is lower farther from the source because:
A. The amount of sound energy present decreases rapidly with outward movement of the sound waves.
B. The frequency of the sound waves decreases as the sound spreads.
C. The same amount of sound energy is spread over a larger area.
D. Most of the sound energy is lost within a few feet of the source.
E. The wavelength of the sound increases with its distance from the source.
A. The amount of sound energy present decreases rapidly with outward movement of the sound waves.
B. The frequency of the sound waves decreases as the sound spreads.
C. The same amount of sound energy is spread over a larger area.
D. Most of the sound energy is lost within a few feet of the source.
E. The wavelength of the sound increases with its distance from the source.
4. The propagation field of a sound produced by an automobile on the ground is half a sphere because:
A. the surface of most highways reflects sounds upward
B. the engine of an automobile is generally located in the front half of the vehicle
C. the metal body of an automobile conducts sound relatively well
D. most highways are surrounded by embankments on either side
E. the sound is not propagated through the ground below the automobile
A. the surface of most highways reflects sounds upward
B. the engine of an automobile is generally located in the front half of the vehicle
C. the metal body of an automobile conducts sound relatively well
D. most highways are surrounded by embankments on either side
E. the sound is not propagated through the ground below the automobile
RC Butler 2022 - Practice Two RC Passages Everyday.
Passage # 241 Date: 16-Jun-2022
This question is a part of RC Butler 2022. Click here for Details
Passage # 241 Date: 16-Jun-2022
This question is a part of RC Butler 2022. Click here for Details
18 Jun 2022, 09:40
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JairajD
Official Explanation
2. According to the passage, sound waves and water waves are similar in all of the following ways EXCEPT:
Explanation
Soundwaves may radiate in a sphere, but water waves radiate only in two dimensions, forming a circle (See the end of paragraph 1).
Answer: A
Explanation
Soundwaves may radiate in a sphere, but water waves radiate only in two dimensions, forming a circle (See the end of paragraph 1).
Answer: A
